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@mbostock
Last active May 13, 2016 20:13
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N-Body Problem
license: gpl-3.0
<!DOCTYPE html>
<meta charset="utf-8">
<style>
body {
background: #000;
}
</style>
<canvas width="960" height="500"></canvas>
<script src="//d3js.org/d3.v3.min.js"></script>
<script>
var canvas = document.querySelector("canvas"),
context = canvas.getContext("2d"),
width = canvas.width,
height = canvas.height;
var n = 200,
tau = 2 * Math.PI,
nodes = d3.range(n).map(function() { return {radius: Math.random() * 8 + 2}; });
var force = d3.layout.force()
.charge(0.5)
.gravity(0)
.friction(1)
.nodes(nodes)
.size([width, height])
.start();
var stroke = d3.scale.linear()
.domain([0, 1])
.range(["steelblue", "brown"]);
force.on("tick", function(e) {
var q = d3.geom.quadtree(nodes), node, i, vx, vy;
context.clearRect(0, 0, width, height);
context.lineWidth = 1.5;
for (i = 0; i < n; ++i) {
q.visit(collide(nodes[i]));
}
for (i = 0; i < n; ++i) {
node = nodes[i];
context.beginPath();
context.arc(node.x, node.y, node.radius - 0.75, 0, tau);
context.strokeStyle = stroke((vx = node.x - node.px) * vx + (vy = node.y - node.py) * vy);
context.stroke();
}
context.beginPath();
for (i = 0; i < n; ++i) {
node = nodes[i];
context.moveTo(node.x, node.y);
context.lineTo(node.x + (node.x - node.px) * 3, node.y + (node.y - node.py) * 3);
}
context.strokeStyle = "#fff";
context.stroke();
force.resume();
});
function collide(node) {
var r = node.radius + 16,
nx1 = node.x - r,
nx2 = node.x + r,
ny1 = node.y - r,
ny2 = node.y + r;
return function(quad, x1, y1, x2, y2) {
if (quad.point && (quad.point !== node)) {
var x = node.x - quad.point.x,
y = node.y - quad.point.y,
l = Math.sqrt(x * x + y * y),
r = node.radius + quad.point.radius;
if (l < r) {
l = (l - r) / (l * 2);
node.x -= x *= l;
node.y -= y *= l;
quad.point.x += x;
quad.point.y += y;
}
}
return x1 > nx2 || x2 < nx1 || y1 > ny2 || y2 < ny1;
}
}
</script>
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